A/F 13.2:1 at WOT - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-25-2008, 01:34 PM   #21
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my car feels slow if I get richer than 12.5:1 in boost. who knows.
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Old 04-25-2008, 01:51 PM   #22
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well, the idea here is that with more air, you can burn more fuel, clearly. but the problem is that the amount of space you're stuffing all the extra air into remains the same, and you have a limited amount of time to make all the combustion happen.

so in a short period of time, you have a very low probability that all the fuel molecules will be next to air molecules required for combustion in the timespan available. you make up for this by adding more fuel, so you increase that probability, with the goal being to use up every last O2 molecule in the chamber. in a n/a motor, you can only get so much in there, so 13.5 is accepted as the ballpark area where you're in the sweet spot between maximizing your chances of leveraging all the O2 molecules, and losing power due to cooler cyls and "crowding" of too many fuel molecules and not enough air (opposite problem of if you injected just enough for stoic). with boost, the tossed around number is 12.5, because at common boost levels, this is probably where people have found that sweet spot to hover around.

in reality, that sweet spot varies with the flow characteristics of your engine, the amount of boost you're running, and the volatility of your fuel.

in any case, the point is that it's POSSIBLE 9though not probable) that a boosted car COULD make max power at 13.2:1 at a given rpm and pressure bin, same way it COULD make max power at 11.4:1. without being on a dyno, you don't know.
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Old 04-25-2008, 01:52 PM   #23
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Well thanks for letting me know I'm going to blow my motor

I'm itching to get the Megasquirt but don't have the $850 right now for that and the injectors so for the tie being I'm running the vortech. But because I'll be adding that in a short while, I'm not going to waste $$ on an o2 clamp or any other band aids. As of now, I'm monitoring a/f with a AEM UEGO and do not have FP or exhaust temp gauges. I'm just making sure I don't hear ping... I was running a helper spring setup on the wastegate to adjust boost now I'm playing with a MBC so I'll try to get it right on 6 psi...

This intercooler is awesome. I've had the car up to 8 psi and 10* timing with no retard and still not knocked whereas pre-intercooler I knocked at 5 psi and 5* timing. Before I get yelled at I won't be running the 8 psi yet. In all honesty, it didn't feel much faster if at all which was most likely due to the fact that the A/F was so shitty due to no fuel control at that boost.

-Ryan
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Old 04-25-2008, 01:57 PM   #24
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if you're that lean maybe swap in the next step up disc. which one are you running? i can't remember if you said.
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Old 04-25-2008, 02:09 PM   #25
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It's the normal 12:1 disc, stock 1.6 injectors. It just maxes out the fuel pump at 70-80ish psi or whatever so it's flowing everything the system can right now. The 13:2 was with ~7psi tapering off to 6 psi. The last thing I need is a higher ratio disc lol.
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Old 04-25-2008, 02:11 PM   #26
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ahh. lol. yeah, that'll do it. you need them megasquirt shitz hotness, son!
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Old 04-25-2008, 02:12 PM   #27
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Quote:
Originally Posted by devin mac View Post
yeah, but weren't you complaining about a pussbag timing map, as well?
BEFORE I fixed the TB, yeah. This is my current map:

SparkMap-Map8.jpg

Ben, I'd ask about the theory behind that, but I think devin explained it. I'll have to spend some more time playing with the fuel map and get a few different curves (one at 12.0 dead, one at 11.6, one at 11.4, etc) to play with when I go to the dyno in May. I also am curious to know whether I can lean it out and pick up power with water injection, on the theory that I'm just using the extra fuel beyond X:1 AFRs to cool the charge, and the WI can take that duty over.
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Old 04-29-2008, 06:08 AM   #28
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gagh.. I tried to read your timing map and saw kpa.. do you always have to view boost in that unit? That could get annoying..
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Old 04-29-2008, 10:57 AM   #29
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kPa isn't nearly as annoying as trying to convert negative inches of mercury to positive pounds per square mothereffin inch!
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Old 04-29-2008, 07:32 PM   #30
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what was your air fuel ratio at 5lbs of boost , and 6lbs of boost? I am curious what the stock greddy fmu, and fuel pump push out a/f ratio wise.
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Old 04-29-2008, 07:35 PM   #31
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my first dyno plot: 7psi, vortech 12:1 FMU, 1.8L injectors, stock pump, bipes acu.
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Old 04-30-2008, 03:24 AM   #32
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Quote:
Originally Posted by Wakaranai View Post
what was your air fuel ratio at 5lbs of boost , and 6lbs of boost? I am curious what the stock greddy fmu, and fuel pump push out a/f ratio wise.
Just put a MBC on the car and tomorrow I will be adjusting in 1 psi increments from 4 psi up to 8 and will take note of the A/F under wot at each boost increment. I'll leave the boost at whichever seems to have the best A/F curve until I go MS. I'll report my findings here.
My info may not be entirely accurate for all 12:1 users though as all of our fuel pumps are in different states of degradation and this disc just maxes the pump out to whatever it is capable of.
-Ryan
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Old 05-01-2008, 05:57 PM   #33
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Okay, update for those wondering how the stock Vortech FMU works. This is on a 1.6 with the fuel system otherwise stock (1.6 injectors).
Went out today and started messing with the boost. Without the MBC, the lowest I can get the wastegate to adjust down to is 4.5-5 psi, if I lengthen the rod any longer it holds the wastegate door open a small bit all the time and I get like 2 psi at 6k rpm.
So, at that 5 psi, 12.5:1 A/F. All the A/F numbers I'm giving are from 4k rpm and up since below that the stock ecu is just freaking out as I have no o2 clamp or such.
So then I started adjusting the MBC.
6 psi peak, 12.6:1 - 12.7:1
7 psi peak, 12.7:1 - 12.9:1
8 psi peak, 13.1:1 - 13.3:1
I say peak because my boost peaks around 4.5k and then tapers off about 2 psi by redline, even with the MBC in place. Oh well.
So, I've got it adjusted to 7 psi right now. Seems like that is the absolute safe max for stock 1.6 fuel systems with the pump maxed out.

-Ryan
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Old 05-01-2008, 07:03 PM   #34
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Hmmm... i don't know about the stock pump maxing out at those boost levels on a 1.6., I've heard of plenty of people running in excess of 200bhp on the stock fuel pump.
My concern would be the injectors, I'm running 5-6psi and the stock injectors are at like 85-90% duty cycle (dyno proven) trying to maitain a 12:1 AFR ratio. I have some 315cc Supra injectors ready to drop in to allow me to run more boost.

Just don't go power crazy and increase the boost to the detriment of your AFR's, the last thing you need is for the engine to go POP!!!!
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Old 05-01-2008, 11:33 PM   #35
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I would put a 190hp in that car, ms or not. Cheap insurance, easy to install, your stock pump must suck.
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Old 05-02-2008, 12:24 AM   #36
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You can buy my extra set of pnp 305cc supra green tops and get better afr's and good idle.

I run those now with the stock fuel pump and begi afpr and get ~12.2 afr all the way to redline at 11 psi. Spend little $ while saving for MS!
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Old 05-02-2008, 05:43 AM   #37
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Quote:
Originally Posted by Braineack View Post


my first dyno plot: 7psi, vortech 12:1 FMU, 1.8L injectors, stock pump, bipes acu.
Question, what were your bipes settings? Im guessing advanced timing to 14* pulling 6*.
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Old 05-06-2008, 02:55 PM   #38
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Quote:
Originally Posted by jim-NA View Post
Hmmm... i don't know about the stock pump maxing out at those boost levels on a 1.6., I've heard of plenty of people running in excess of 200bhp on the stock fuel pump.
My concern would be the injectors, I'm running 5-6psi and the stock injectors are at like 85-90% duty cycle (dyno proven) trying to maitain a 12:1 AFR ratio. I have some 315cc Supra injectors ready to drop in to allow me to run more boost.

Just don't go power crazy and increase the boost to the detriment of your AFR's, the last thing you need is for the engine to go POP!!!!
Well obviously changing the inectors changes the whole ball game. I'm talking about what the stock 1.6 pump can supply on a stock 1.6 fuel system i.e. 1.6 injectors. I'm getting a MSPNP and 460cc inejctors. So I will never need to upgrade my pump since with full control over those injectors I will never need to go with any more fuel pressure than stock, which the stock pump can supply with plenty of head room.
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Old 05-06-2008, 04:39 PM   #39
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Andrew, it absolutely won't make max power at stoich. Tip into boost at 14.7:1, then retune to tip in at 13:1 then let me know which feels more powerful.
Correct me if im wrong but i believe that in "maximum boost" it says that mean best torque is around 12.3-12.5:1.
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